1. Field of the Invention
This invention relates generally to bulk material belt conveyor systems. More specifically, this invention pertains to training idlers for controlling belt tracking on conveyor belt systems.
2. General Background Technology
All bulk material belt conveyor systems comprise a belt that extends in a continuous loop around rollers. The upper portion of the continuous loop can be referred to as a transfer run and the lower portion of the continuous loop can be referred to as a return run. To maintain proper belt tracking, bulk material conveyor belt systems are typically provided with training idlers. Such training idlers are utilized on both transfer and return runs and typically take the form of one or more rollers mounted on a roller support frame that is pivotable about a vertical (or near vertical) axis. When a conveyor belt tracks of center, the uneven drag or friction acting on the training idler causes the roller support frame to pivot about the axis in manner such that the rollers no longer rotate about axes that are perpendicular to the direction of belt travel. As such, the rollers act to redirect the belt back into alignment. In some cases, outrigger rollers or shoes are provided at the opposite ends of the roller support frame to assist in pivoting the support frame. The shoes or the outrigger rollers extend above the edges of the belt and are spaced from each other by a distance that is greater than the belt width. When the belt is out of alignment enough to contact one of the shoes or one of the rollers, the drag generated by the shoe or roller creates additional torque on the roller support frame that assists in pivoting the support frame.
In practice, bulk material conveyor belt systems often track off center for various reasons including off-center loading of the bulk material and misalignment of the conveyor components or structure. In some cases, belts track off center to one specific side for an appreciable duration of time. In such situations, maintenance workers have been known to tie off the training idlers to other structure so as to force their roller support frames to be skewed off center by at least a set amount. This is often done with wire, which creates a danger to the workers because it can become entangled in moving components of the conveyor belt systems.